Busan, South Korea – As Busan’s skyline grows and its urban sprawl continues, the city faces a looming crisis underground. Beneath the bustling streets and expanding neighborhoods lies an aging water infrastructure—over 40% of Busan’s water pipes are now more than 30 years old, susceptible to frequent bursts, leaks, and even collapse. These weaknesses in the city’s foundation are increasingly leading to dangerous sinkholes, threatening both public safety and the integrity of essential infrastructure.
The situation has become more precarious as the city prepares to expand its subway network, a key project aimed at alleviating traffic congestion and supporting sustainable urban growth. However, this plan comes with significant risks. As seen in other global cities, the convergence of old water pipes, weakened ground conditions, and intensive tunneling could accelerate the formation of sinkholes and worsen existing infrastructure problems.
Busan is not alone in facing such dilemmas. Cities like New York, London, and Tokyo have grappled with similar infrastructure challenges, balancing modern transportation needs against the realities of an aging underground system. As climate change adds yet another layer of complexity—bringing unpredictable weather patterns and intensifying storms—the city must tread carefully. Subway expansion, while essential, could exacerbate existing vulnerabilities if not managed with foresight, innovation, and a comprehensive understanding of the risks involved.
Busan’s Infrastructure: Aging Pipes and Sinkholes
Busan’s water infrastructure, built to support the city’s rapid post-war expansion, now faces the inevitable strain of time. Approximately 41% of the city’s water pipes are over three decades old, many of them constructed from materials no longer deemed durable or safe for modern usage. As these pipes corrode and crack, they contribute to a growing crisis that goes largely unseen but increasingly felt by residents.
In recent years, the consequences of this aging network have become more visible—and more dangerous. In districts like Sasang-gu, Haeundae and Nam-gu, a number of sinkholes have appeared, some large enough to swallow entire sections of roads and threaten nearby buildings. The cause is often traced back to undetected leaks in the underground water pipes. As water seeps through these cracks, it slowly erodes the surrounding soil, weakening the ground until it can no longer support the weight above, leading to sudden collapses.
Busan’s geographical characteristics exacerbate the problem. The city’s coastal location and hilly terrain mean that ground stability can fluctuate dramatically with seasonal rains and typhoons. Heavy rainfall, a regular feature of the Korean summer, can infiltrate the weakened soil around leaking pipes, accelerating the erosion process and increasing the likelihood of sinkholes. Additionally, as the city continues to urbanize, the pressure on both above-ground and underground infrastructure is intensifying, with more buildings, roads, and subway lines putting increased stress on an already compromised system.
Residents have become familiar with the sight of emergency road closures and repair crews hurriedly fixing pipe bursts or repairing newly formed sinkholes. But the cost of these reactive measures is significant, not only in financial terms—annual emergency repair costs are rising—but also in terms of public safety. In 2021 alone, dozens of incidents involving ground subsidence were reported, with many linked directly to aging water pipes.
Busan is now at a critical juncture. The city can no longer afford to ignore its deteriorating infrastructure, particularly as the effects of climate change, such as more frequent and intense storms, begin to compound the risks. The upcoming expansion of the subway network adds urgency to the situation. Without addressing the root causes of these problems—namely, the failing water pipes and unstable ground conditions—subway construction could intensify the city’s vulnerabilities.
Infrastructure and Underground Construction Challenges
The challenges Busan faces with its aging water infrastructure and expanding subway system are not unique. Cities across the globe, from New York to Tokyo and London, have encountered similar issues as they attempt to modernize transportation networks while grappling with outdated, often crumbling, underground utilities. Understanding how these global cities have addressed—or struggled with—such problems offers critical lessons for Busan.
United States: New York and Los Angeles
In the United States, New York City presents one of the starkest examples of the intersection between aging infrastructure and the demands of urban growth. With water pipes over a century old in many neighborhoods, the city experiences an average of 400 water main breaks annually. In 2019, a major water main burst flooded streets in Manhattan, causing significant disruptions to both traffic and the city’s subway system. Similar to Busan, water leaks in New York have contributed to ground instability, occasionally resulting in sinkholes that not only threaten public safety but also require expensive emergency repairs.
The extensive underground subway network in New York, one of the largest in the world, presents its own set of complications. Tunneling through dense urban areas, contractors must often work in proximity to ancient pipes and utilities. During the construction of New York’s Second Avenue Subway, for example, engineers encountered numerous obstacles, including deteriorating pipes and unstable ground. The result was years of delays and ballooning costs, issues that Busan could potentially face without proper planning and infrastructure upgrades.
In Los Angeles, the situation is no less severe. The city’s rapid urban expansion over the last century has put immense pressure on aging water pipes and sewer systems. Like New York, Los Angeles has seen frequent water main breaks and sinkholes, often occurring during subway expansions or other major infrastructure projects. In 2014, a major water main rupture on Sunset Boulevard created a 15-foot-deep sinkhole, flooding the surrounding area and highlighting the risks posed by neglected infrastructure during times of heavy urban development.
London: Victorian-Era Infrastructure
Across the Atlantic, London’s struggle with aging infrastructure echoes many of the same concerns found in Busan. Much of London’s water system was built during the Victorian era, meaning that significant portions of the pipe network are over 150 years old. With this in mind, it is unsurprising that leaks and bursts occur frequently, leading to water loss and ground instability. London’s bustling underground transport system—the Tube—has faced its own challenges due to the city’s aging infrastructure. Water leaks in the underground tunnels, often exacerbated by old pipes, have led to service interruptions and costly repairs.
London’s response has involved phased infrastructure upgrades, with the replacement of old pipes and improved monitoring systems. However, these efforts are expensive and slow, given the extent of the outdated network and the need to minimize disruptions in one of the world’s busiest cities. The delays and rising costs associated with London’s efforts offer a cautionary tale for Busan as it considers how best to balance infrastructure repair with subway expansion.
Tokyo: A Model of Proactive Infrastructure Management
On the other end of the spectrum, Tokyo stands out as a model of proactive infrastructure management. Recognizing the dangers of aging water pipes and the risks posed by Japan’s frequent earthquakes, the city has implemented a comprehensive plan to upgrade its water system. Tokyo’s water pipes have been progressively replaced with earthquake-resistant materials, reducing the likelihood of bursts and leaks that could destabilize the ground.
Moreover, Tokyo has integrated smart water management systems that use sensors to detect leaks in real time, allowing the city to address small issues before they become major problems. This approach has not only improved the city’s resilience but also ensured that its subway system—one of the most extensive in the world—operates without frequent interruptions due to infrastructure failures. Tokyo’s forward-thinking policies offer valuable insights for Busan as it seeks to modernize its subway network while avoiding the pitfalls of failing infrastructure.
Environmental and Climate Impact Considerations
Busan’s geographic position on the southern coast of the Korean Peninsula exposes it to heavy seasonal rains, typhoons, and rising sea levels—weather patterns that are becoming more severe due to climate change. These extreme weather events have a direct impact on the city’s underground infrastructure. In the rainy season, water pipes and the surrounding ground are further stressed by excessive water infiltration, increasing the risk of leaks, pipe bursts, and ground subsidence. Climate models project that these weather patterns will only intensify in the coming decades, making Busan’s infrastructure all the more vulnerable if proactive measures are not taken.
The potential for flooding is particularly concerning when it comes to subway systems. Cities around the world, such as New York and London, have experienced severe disruptions in their subway networks due to flooding caused by heavy rainfall and rising groundwater levels. In New York, for instance, the subway system faced unprecedented damage during Hurricane Sandy in 2012, when floodwaters overwhelmed tunnels and stations, causing billions of dollars in damage and shutting down large sections of the network for extended periods. Busan faces similar risks, especially as it expands its subway system while grappling with already weak underground conditions.
Building new subway lines requires an immense amount of construction materials such as steel, cement, and concrete, all of which carry significant embodied emissions—the greenhouse gases emitted during the extraction, production, and transportation of these materials. Globally, subway construction is responsible for hundreds of millions of tons of CO₂ emissions due to the energy-intensive processes required to create the materials used in tunnels, stations, and ventilation systems. A study of global subway systems found that, in cities like Shanghai and Beijing, the embodied emissions from subway construction are equivalent to nearly 23 years’ worth of operational emissions from the system.
Busan’s subway expansion will likely contribute a substantial share of carbon emissions during construction, posing a challenge for the city’s efforts to meet national and international climate targets. To mitigate these environmental impacts, Busan must explore the use of low-carbon building materials and energy-efficient construction methods. Additionally, incorporating renewable energy sources into subway operations, such as solar panels at stations or energy-efficient lighting and ventilation systems, could help offset the carbon footprint of construction.
Subway systems, by nature of their underground design, are particularly vulnerable to flooding. As New Yorkexperienced during Hurricane Sandy and London has seen during flash floods, even well-engineered subway systems are not immune to the forces of nature. Busan, with its history of typhoons and heavy rainfall, must take preemptive steps to ensure the resilience of its new subway lines. Building waterproof barriers, installing high-capacity drainage systems, and implementing early warning systems for flood risk are some of the strategies that can reduce the potential for catastrophic flooding.
Sustainable Solutions for Infrastructure and Subway Development
As Busan faces the dual challenges of expanding its subway network and addressing the issues caused by aging water infrastructure, it must explore innovative and sustainable solutions to prevent further damage and ensure the long-term resilience of the city’s development. Drawing from both global best practices and emerging technologies, Busan can implement a range of strategies to mitigate the risks associated with subway construction and aging pipes, while also building a more sustainable urban environment.
One of the most effective strategies in addressing infrastructure vulnerabilities before they lead to major incidents is the implementation of smart monitoring systems. These systems, already in use in cities like Tokyo and Singapore, employ advanced sensors to detect leaks in water pipes or shifts in soil that could indicate potential ground instability. These technologies allow engineers to address small problems before they escalate into larger ones, such as sinkholes or pipe bursts.
For Busan, integrating smart monitoring into both the existing water infrastructure and the subway construction process would be a crucial preventive measure. Sensors installed along major water pipes can detect early signs of leaks or pipe degradation, triggering real-time alerts for maintenance teams. Similarly, during subway tunneling, sensors can monitor vibrations and ground movement, minimizing the risk of ground instability due to construction activities. By implementing such technologies, Busan can reduce both the immediate risks of subway expansion and the long-term costs of maintaining its aging infrastructure.
In addition to smart water management, geotechnical monitoring systems should play a key role in Busan’s infrastructure plans. Geotechnical sensors, including ground-penetrating radar and seismic monitoring systems, can provide valuable data on the stability of the ground in areas with a history of water leaks or sinkholes. By using these tools, engineers can track underground shifts, identify high-risk areas, and proactively take steps to stabilize the ground before major construction begins.
This type of monitoring is especially important in a city like Busan, where coastal geography and frequent rainstorms make the ground particularly vulnerable to erosion. Hong Kong, for instance, has used geotechnical monitoring extensively to track slope stability and prevent landslides during construction projects in its hilly terrain. Busan could adopt similar technologies to better manage the risks posed by its own landscape and infrastructure challenges.
Before embarking on large-scale subway expansion, Busan must prioritize pre-construction upgrades to its aging water pipes. Much like London did during its Tube expansion projects, Busan should replace or reinforce critical sections of its water infrastructure, particularly those that run close to planned subway tunnels. Failure to do so could result in leaks or bursts during construction, which could not only delay subway projects but also exacerbate ground instability.
Although upgrading existing water infrastructure is costly, the long-term savings in terms of avoided emergency repairs and service disruptions far outweigh the initial investment. In Tokyo, phased upgrades of water pipes, using earthquake-resistant materials, have significantly reduced the frequency of pipe bursts, especially during subway construction. By following a similar model, Busan can strengthen its infrastructure and minimize the risks of disruptions during future subway expansions.
Another important framework for Busan to consider is the Deep City Method, a sustainable urban planning approach developed to manage the competing demands of underground space. As cities around the world become denser, the need to balance the use of underground space for utilities, transportation, and resource management becomes increasingly important. The Deep City Method emphasizes careful planning to avoid conflicts between different underground systems, ensuring that water pipes, subways, and other utilities can coexist without threatening the stability of the city’s foundation.
This method has already been successfully applied in Switzerland and is gaining traction in other cities with dense urban cores, like Shanghai and Paris. For Busan, adopting the principles of the Deep City Method could provide a clear framework for sustainable development thatSorry about that! Let me continue and finish the final section.
Another important framework for Busan to consider is the Deep City Method, a sustainable urban planning approach designed to balance the competing demands of underground space use. As urban areas become denser, it becomes crucial to manage underground infrastructure carefully. The Deep City Method, successfully implemented in cities like Switzerland and explored in Shanghai and Paris, advocates for a structured approach to the development of underground spaces, ensuring that utilities like water pipes, subways, and other underground infrastructure coexist without conflict or undermining each other.
Busan stands at a pivotal moment in its urban development. As the city continues to grow, the need for a modern, efficient subway system is clear, but so too is the need to address the vulnerabilities of its aging infrastructure. By investing in smart monitoring systems, upgrading its water pipes before construction, and adopting forward-thinking planning methods like the Deep City Method, Busan can ensure that its subway expansion not only supports its immediate needs but also lays the groundwork for a sustainable, resilient future.
Sustainability is not just an environmental buzzword—it is a necessity in ensuring that Busan’s infrastructure can withstand the pressures of urbanization and climate change. With careful planning and the right investments, Busan can turn this moment of challenge into an opportunity for innovative urban growth.
